The present invention relates to the field of angioplasty. In particular, the present invention relates to a balloon catheter which permits prolonged inflation of the balloon within a blood vessel, such as a coronary artery, without blocking blood flow by utilizing passive perfusion.
Angioplasty has gained wide acceptance as an efficient, effective and alternative method of treating constrictions caused by undesirous tissue growth or lesions on the inner walls of the blood vessels. Such tissue growth or lesions cause a narrowing of the blood vessels called a "stenosis" which severely restricts or limits the flow of blood. In the most widely used form of angioplasty, a dilatation catheter, which has an inflatable balloon at its distal end, is guided through the vascular system. With the aid of fluoroscopy, a physician is able to position the balloon across the stenosis. The balloon is then inflated by applying fluid pressure through an inflation lumen of the catheter to the balloon. Inflation of the balloon stretches the artery and presses the stenosis-causing lesion into the artery wall to remove the constriction and re-establish acceptable blood flow through the artery.
One disadvantage of many balloon catheters of the prior art is the complete occlusion of the blood vessel that results while the balloon is inflated. Prolonged complete blockage of a blood vessel poses serious risk of damage to the tissue, downstream from the occlusion, which is deprived of oxygenated blood. This consequence poses a severe limitation on the length of time the balloon can remain expanded within an artery to effectively treat the stenosis. Longer inflation times increase the probability that the artery will remain open after the catheter is removed.
Various methods for providing passive perfusion of blood through or past the inflated balloon are found in the following prior art references: Guiset U.S. Pat. No. 4,183,102; Baran et al. U.S. Pat. No. 4,423,725; Sahota U.S. Pat. No. 4,581,017; Hershenson U.S. Pat. No. 4,585,000; Horzewski et al. U.S. Pat. No. 4,771,777; Mueller et al. U.S. Pat. No. 4,790,315; Songer et al. U.S. Pat. No. 4,892,519; Goldberger U.S. Pat. No. 4,909,252; Sogard et al. U.S. Pat. No. 4,944,745; Sahota U.S. Pat. No. 4,983,167 and European Patent Application 0 246 998; Boussignac et al. U.S. Pat. No. 5,000,734; Patel U.S. Pat. No. 5,000,743; and Bonzel U.S. Pat. No. 5,002,531.
A disadvantage of prior tubular-shaped, perfusion balloon catheters is the additional manufacturing steps necessary to connect outer and inner skins of the balloon to create a perfusion passage between the up-stream side of the balloon and the down-stream side of the balloon. Another disadvantage is the risk of interrupted integrity of the balloon at the seams created by the connection of outer and inner skins. Additionally, tubular-shaped balloons of the prior art are relatively stiff due to the seams and internal support structures. There is still a need in the field, therefore, for a balloon catheter with good flexibility and a perfusion cavity which, when inflated within an artery, permits good arterial blood flow, and yet is capable of being manufactured with relative ease and minimal cost.